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Production of glass–ceramics from heavy metal gypsum and pickling sludge
Pan, D. A.; Li, L. J.; Yang, J.; Bu, J. B.; Guo, B.; Liu, B.; Zhang, S. G. & Volinsky, A. A.
Abstract
The aim of this investigation was to propose a
preparation method of glass–ceramics derived from heavy
metal gypsum and pickling sludge, as well as stabilization
of Pb, Zn, Cd, As, Hg, Cr and Ni heavy metals. The process
consists of the following two stages: the desulfurization of
heavy metal gypsum and the preparation of glass–ceramics.
Heavy metal gypsum was desulfurized by excess glass
powder at 1,473 K and formed calcium silicate and silicon
dioxide as intermediate products. The intermediate products,
pickling sludge and small amounts of CaO and MgO
were used as major raw materials for preparing parent
glass. Glass–ceramics was produced by conventional
heating method, which included a nucleation stage (973 K,
2 h) and a crystallization stage (1,173 K, 1 h). The main
crystalline phase of the obtained glass–ceramics is akermanite
(Ca2MgSi2O7). A high microhardness of 5.3 GPa
and a bending strength of 206 MPa, as well as a water
absorption lower than 0.13 % were obtained. The leaching
of toxic elements in glass–ceramics was much lower than
the Environmental Protection Agency 1311 method
requirement.
Keywords
Heavy metal gypsum; Pickling sludge; Glass–ceramics; Desulfurization
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